1. Field of the Invention
The present invention relates generally to analytical methods. In particular, the present invention relates to a fertilization test method and apparatus.
2. Description of the Prior Art
For compliance with the federal Clean Water Act, municipalities and private business have the task of measuring the contaminant level in surface water and discharge streams. One test used to determine contaminant levels involves a fertilization test, which determines the ratio of fertilized to unfertilized sea urchin (Arbacia punctulata) eggs and compares that ratio with a control sample.
A lab technician traditionally uses a pipette to dispense a water sample onto a microscope slide and then covers the sample with a slide cover slip. The technician then views the water sample through a bright field microscope at about 100× magnification. The technician visually scans the water sample looking for fertilized eggs as indicated by a fertilization membrane surrounding the egg. The presence of a membrane, or halo, around the outside of the egg confirms that the sea urchin egg has been successfully fertilized.
The water sample may contain between 30 and 45 counting chambers, each of which contain many sea urchin eggs of between 100-250 μm in diameter. The lab technician uses the microscope's micropositioner to move the slide and analyze the entire sample for sea urchin eggs, typically examining at least 100 sea urchin eggs for the presence of a fertilization membrane, which may be between 1 and 10 μm thick. The lab technician manually counts the number of fertilized and unfertilized eggs in the sample. The technician reports the percentage of fertilized eggs in each sample and compares that percentage to control samples. A difference between the percentage of fertilized eggs in the sample and the percentage of fertilized eggs in the control sample indicates the presence of toxins in the water sample. According to Environmental Protection Agency guidelines, a representative sample should include a count of at least 100 eggs.
Because a fertilization test is performed manually, it requires significant time of an employee having the expertise and training to complete the test. A trained lab technician typically requires between one and two hours to complete a fertilization test for each water sample. While five to ten tests may be performed at one time, a lab technician may analyze many samples per customer.
Other analytical methods have been used to analyze cells in related fields. A flow cytometry system or “FACS machine” sort cells based on the size or growth of the cell. This analytical method is frequently used for antibody coupling analysis in DNA and red blood cells. Hematoxylin and eosin stain techniques, sometimes referred to as an HE section, use red and blue dyes to emphasize various components of cell structure based on color differences of the cell components. The HE section technique has been automated in medical diagnosis equipment.